Crystallization Investigations of Ge‐Rich GST Cells Using In Situ Thermal Pulses Coupled With STEM–EDX and HR‐TEM Analyses

The crystallization of initially amorphous Ge‐rich GeSbTe nanostructures is investigated using fast thermal pulse heating, coupled with in situ scanning transmission electron microscope–energy dispersive spectroscopy (STEM–EDX) and high resolution (HR)‐Transmission electron microscopy (TEM) analyses. Chemical analysis reveals a TeGe interdiffusion mechanism occurring at the bottom interface between the Ge‐rich GST (GGST) layer and the underlayer (UL). The initially Ge‐rich cell shows increasing Te‐enrichment as the temperature increases. The onset of crystallization was found to start at 350°C with pure cubic Ge grains appearing first, followed by cubic GST at 390°C. Initially localized at the interfaces, the crystallization of both phases spreads heterogeneously throughout the cell. The spatial distribution of grains is compared with the variations in chemical composition at the nanometric scale.